Metallic cross connect switching systems have been in existence since the advent of telephony. Legacy switching systems require an operator to manually connect calls between an ingress port and an egress port. In general terms, an “ingress port” refers to an input, and an “egress port” refers to an output. Since human interaction is often inefficient and subject to errors, next generation switching systems were designed for use without operators. Thereafter, with advancements in the field of metallic switching, cross bar switching systems were implemented.
There are many problems and disadvantages with conventional switching systems. For example, the equipment used with such systems are quite large and would typically occupy a large space. In addition, the conventional metallic cross connect switching was labor intensive and often error prone. Moreover, most conventional switching systems are designed such that no more than, for example, 25% of the maximum calls can be serviced. In other words, when the conventional switching system is servicing 25% of the maximum number of calls, additional calls will be “blocked” until the service level is below 25%.
FIG. 1 is a simplified block diagram of a conventional single stage cross connect switching system. This figure illustrates the most basic architecture. The switching system 2 consists of a single stage switching matrix 4 connecting the ingress ports 6 with the egress ports 8. The ingress ports are designated as Ig1, Ig2, Igi, . . . Ign, and the egress ports are designated as Eg1, Eg2, Egi, . . . Egm. Each ingress and egress port consists of a pair of physical wire (i.e., 2 leads). The ingress ports 6 can also be connected to a Main Distribution Frame (“MDF”) (not shown) in a Central Office (“CO”). The egress ports 8, likewise, can be connected to another equipment, which may be another MDF.
In the single stage cross connect switching system, n and m each represents the number of ingress and egress ports, respectively. The n and m values can range from, for example, 10 to 100,000. The capacity of a cross connect system is generally referred to as n×m ports. In fact, depending on the value of n and m ports, the cross connect systems are known as follows:                when n is greater than m, it is called a “Concentration System”;        when n equals m, it is called a “Squared Matrix System”; and        when n is less than m, it is called an “Expansion System.”        
Another notable characteristic of a cross connect switching system is its ability to make connections from ingress to egress ports. When any ingress port can connect to only some egress ports, this is known as a “Blocking System.” When any ingress port can connect to any egress port, this is known as a “Non-blocking System” or “Any-to-Any System.”
FIG. 2 illustrates a conventional cross connect element. This basic building block is a basic element in a metallic cross connect system. The element 12 includes two input leads In1, In2, two output leads Out1, Out2, and a control lead Ctrl. A fundamental design characteristic is the interconnection of these leads with each other. The interconnections can take place at different levels including: (1) device level—interconnecting basic elements to form a packaged device; (2) board level—interconnecting devices to form a circuit board; (3) shelf level—interconnecting boards to form a sub-system or system; (4) rack level—interconnecting shelves to form a sub-system or system; and (5) inter-rack level—interconnecting racks to form a sub-system or system. The requirement for the number of basic building elements and the associated packaging level for device, board, shelf, rack, and inter-rack are dictated by the number of ports required for the overall system. To illustrate the number of basic cross connect elements 12 required to implement a single switching stage system is as follows: (1) for a 100×100 ports system, 10,000 cross connect elements are required; (2) for a 1000×1000 ports system, 1,000,000 cross connect elements are required; and (3) for 10,000×10,000 ports system, 100 million cross connect elements are required. As can be appreciated, the number of basic elements required is approximately equal to the product of the number of ingress ports and the number of egress ports.
FIG. 3 illustrates a simplified block diagram of a conventional multi-stage cross connect switching system. The multi-stage cross connect switching system can be used to reduce the number of basic elements for a given n×m ports systems. FIG. 3 illustrates an architecture using multi-switching stages to reduce the number of basic switching elements. It consists of an Ingress-Switching Stage 22, Core-Switching Stage(s) 24, an Egress-Switching Stage 26, the Inter-Stage Connections 32a, 32b, and the ingress 6 and egress ports 8 for connection to equipments outside the system. Also illustrated are the connections within each switching stage. This multi-switching stage system is used to reduce the number of cross points, but the disadvantage is that there may be a loss of system performance. It can be appreciated that conventional interconnect systems can be quite complex, prone to error during installations and maintenance repair, leading to potential reliability and system performance problems.
As detailed above, the conventional interconnect methods and techniques are inadequate and unworkable because of their physical interconnection tasks are enormous and extremely complex. One of the key challenges today is to design and develop the physical interconnections for the overall system in an efficient and simplified manner. Accordingly, there is a need for a physical architecture to efficiently implement the interconnection requirements demanded by the design of high density metallic cross connect switching systems.